Compositions comprising a fluorine-containing polymer have excellent characteristics, such as heat resistance, chemical resistance, solvent resistance, and insulation. Therefore, such compositions are used in various products requiring heat resistance. Specifically, the compositions are used in coating materials and various formed articles such as electronic equipment, vehicles and electric wires. The coating films and formed articles and the like made from the coating materials may be exposed to high temperatures during use, as well as during production. Therefore, starting compositions are needed to be prevented from coloring at high temperatures and needed to be further improved in thermal stability, heat aging resistance, and the like.
For example, coating materials including a fluorine-containing polymer generally need to be melted by heating for being formed into a film after being applied to an object. In order to form a corrosion resistant lining, the steps of applying and melting by heating are repeated several times because the lining needs to have a certain degree of thickness. The fluorine-containing polymer has heat resistance. However, the fluorine-containing polymer heated at a temperature in the vicinity of the melting point or higher for a long time may be thermally degraded, and colored, and may become brittle or be bubbled. Therefore, it is known that thermostabilizers are used in coatings.
Patent Document 1 discloses a fluororesin powder for rotational forming containing copper or a copper compound, as a technique in which a metallic compound is used as a thermostabilizer. Patent Document 2 discloses a powder composition including ethylene/tetrafluoroethylene copolymer and a thermostabilizer. The thermostabilizer is at least one selected from the group consisting of copper compounds, tin compounds, iron compounds, lead compounds, titanium compounds, and aluminum compounds. Patent Document 3 discloses a fluororesin composition containing, as a stabilizer, at least one of a carbon black powder, an organic sulfur compound, an amine antioxidant, fine powders of zinc, tin, cobalt, nickel, or iron.
Patent Document 4 discloses a powder coating material including a copolymer comprising ethylene and tetrafluoroethylene, and a stabilizer containing no metallic element, as a technique in which a metallic compound is not used as a stabilizer. Further, Patent Documents 5, 6, and 7, for example, disclose, as a composition for coating, a composition including a metallic element for improving adhesion between a coating film and a substrate, but not for being used as a stabilizer.
Patent Document 8, for example, discloses, as a fluororesin including a metallic element, a formed product comprising a copper-containing fluororesin in which a carboxyl group of a fluoroolefin polymer having —CF2COOH is converted into a copper salt. Such copper is included for intercepting a near infrared ray, but not for being used as a stabilizer.
As a technique for adding an additive to a composition to be made into a formed article, Patent Document 9 discloses an ethylene-4 fluoroethylene copolymer composition improved in thermal stability. The composition is prepared by adding copper or a copper compound to ethylene-4 fluoroethylene copolymer and mixing them.
Patent Document 10 discloses a high-temperature grease composition containing at least one or more of (i) fluoro silicone oil, (ii) fluororesin thickeners, (iii) additives such as a modified undecane mixture, a modified butane, Cu phthalocyanine, and Ca sulfonate, as fluorine grease which is prevented from degradation under high temperature conditions and excellent in heat resistance having long-term stability. However, Patent Document 10 does not disclose a cobalt compound at all.
Patent Document 11 discloses a heat-resistant-resin product including a resin layer in which granular materials are dispersed. The product provides carbon dioxide reduction effects by including a metalloporphyrin complex in liposome as the granular materials.    Patent Document 1: JP 3135354 B    Patent Document 2: JP 2006-206637 A    Patent Document 3: JP 55-133442 A    Patent Document 4: JP 2003-3111 A    Patent Document 5: JP 52-126431 A    Patent Document 6: JP 61-25750 B    Patent Document 7: JP 58-141252 A    Patent Document 8: JP 2000-103812 A    Patent Document 9: JP 52-25850 A    Patent Document 10: JP 8-143883 A    Patent Document 11: JP 2007-204666 A